In clutches used to interrupt traction, i.e. during a gear shift an input shaft is separated from a prime mover by a clutch, it is possible to introduce a gear by engaging a clutch of the above described kind, by sliding selector teeth of a sliding sleeve into coupling teeth of a clutch body fastened to a transmission component to be coupled, such as a gear wheel or a transmission housing. In an engaged state, the torque is transmitted, via the clutch body, the coupling teeth, the selector teeth, the sliding sleeve and the sleeve guide from one transmission component to another transmission component, such as a gear wheel or a shaft or is supported on the transmission housing. The engaged gear determines the reduction ratio and thus the rotational speed ratio between the input shaft and an output shaft of the transmission. The non-coupled transmission components, e.g. freely rotating toothed wheels in constant engagement of the other gears, rotate at a differential rotational speed corresponding to their ratio to the engaged transmission components. If when changing from one gear to another, the parts to be coupled during the gear change are brought to a rotational speed almost equal, the selector teeth of the sliding sleeve can mesh in the coupling teeth of the clutch body to be engaged.
A synchronization device serves for this purpose. It essentially comprises friction surfaces, such as a friction cone on the clutch body, and friction surfaces, such as a countercone, on the synchronizing ring which in addition has locking teeth. The synchronizing ring rotates with the sliding sleeve, but it can rotate relative to the sliding sleeve between two stops around a limited rotation angle in order that a locking device, e.g. locking teeth on the synchronizing ring, is brought to a locking position.
If the sleeve is moved in direction of the clutch body to be engaged, the synchronizing ring is pressed with its countercone by flexible detent means against the friction cone of the clutch body. At the same time, the synchronizing ring rotates relative to the sleeve so that inclined surfaces on the front side of the selector teeth strike upon corresponding locking surfaces of the locking teeth. Thereby an axial force is exerted upon the synchronizing ring and the friction surfaces. The shifting force simultaneously produces, via the inclined surfaces, a restoring force upon the synchronizing ring. During synchronous speed of the parts, the force outbalances the peripheral force, acting on the friction surfaces, and brings the synchronizing ring to a central position in which the sleeve can be completely engaged.
Those clutches are known already, namely, from DE 34 445 62 A1 for clutches of planetary design and from DE 34 446 70 A1 for clutches of countershaft design.
In clutches where the gear shift is carried out from an engaged state via a neutral position to another shift position, under certain conditions of operation, it can occur that during the gear shift the sliding sleeve almost unhindered crosses the synchronizing ring that has not, or not enough, been turned to locking position and thereby the selector teeth touch the clutch teeth, which causes unpleasant noises and wear.
The problem, on which the invention is based, is to prevent noises and wear.